JP2022150085A - Cooling structure for motor - Google Patents

Abstract

To provide a cooling structure of a motor capable of improving uniformity of cooling of a heating part.SOLUTION: In a radial view of a first cooling pipe 30A and a second cooling pipe 30B, the farther discharge ports 50 are positioned separating away from a rotation axis CL1, the larger diameters the discharge ports have, respectively. Therefore, the farther the discharge ports are positioned away from the rotation axis CL1, the more the discharge ports can discharge, respectively. In such a case, the first cooling pipe 30A and the second cooling pipe 30B are capable of securing supply amounts of coolant more for locations where the coolant is harder to flow.SELECTED DRAWING: Figure 4

Description

The present invention relates to a cooling structure for an electric motor.

Patent Literature 1 describes a cooling structure that supplies and cools an electric motor with oil. An electric motor includes a rotating shaft extending along a rotating shaft, a rotor provided on the rotating shaft, and a stator provided around the rotating shaft with respect to the rotor. The cooling structure comprises cooling tubes arranged above the stator.

Japanese Unexamined Patent Application Publication No. 2011-217438

In the cooling structure for the electric motor described above, the cooling pipe is formed with a plurality of outlets, and the cooling medium is supplied to the heat-generating part from the outlets. However, in the conventional cooling structure of the electric motor, there is a problem that the cooling medium cannot be uniformly supplied to the heat generated. Therefore, there is a need to improve the uniformity of cooling the heat-generating part.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cooling structure for an electric motor that can improve the uniformity of cooling of a heat generating portion.

A cooling structure for an electric motor according to the present invention is for cooling an electric motor comprising a rotating shaft extending along a rotating shaft, a rotor provided on the rotating shaft, and a stator provided around the rotating shaft with respect to the rotor. A cooling structure comprising a first cooling pipe and a second cooling pipe arranged in parallel so as to extend in an axial direction above a stator, the first cooling pipe and the second cooling pipe A plurality of discharge ports for discharging the cooling medium flowing through the pipes are formed at predetermined positions in the axial direction. The diameter of the ejection port is larger.

A cooling structure for an electric motor according to the present invention includes a first cooling pipe and a second cooling pipe arranged in parallel so as to extend in an axial direction above a stator. Also, a plurality of discharge ports for discharging the cooling medium flowing through the pipes are formed at predetermined positions in the axial direction of the first cooling pipe and the second cooling pipe. Therefore, each of the first cooling pipe and the second cooling pipe can supply the cooling medium to the heat generating portion at a plurality of locations by discharging the cooling medium from the plurality of discharge ports. Here, when the first cooling pipe and the second cooling pipe are viewed from the radial direction, the diameter of the discharge port increases with distance from the rotating shaft. Therefore, the ejection amount can be increased as the ejection port is farther from the rotating shaft. In this case, the first cooling pipe and the second cooling pipe can ensure the supply amount of the cooling medium at a location where the cooling medium flows more slowly. As described above, it is possible to improve the uniformity of cooling of the heat generating portion.

At least three discharge ports may be formed at predetermined positions in the axial direction of the first cooling pipe and the second cooling pipe. In this case, the first cooling pipe and the second cooling pipe can suitably adjust the supply mode of the cooling medium to the heat-generating part with at least three outlets.

A plurality of discharge ports formed at predetermined positions in the axial direction of the first cooling pipe and the second cooling pipe may be formed at different positions in the axial direction with respect to other adjacent discharge ports. In this case, it is possible to suppress a decrease in the strength of the first cooling pipe and the second cooling pipe due to the adjacent outlets being densely packed.

ADVANTAGE OF THE INVENTION According to this invention, the cooling structure of the electric motor which can improve the uniformity of cooling of a heat-generating part can be provided.

It is the figure which looked at the cooling structure which concerns on embodiment of this invention from the axial direction. FIG. 2 is a cross-sectional view taken along line II-II shown in FIG. 1; FIG. 2 is a diagram showing the electric motor in a state where a front retainer is removed from the state shown in FIG. 1; It is the figure which looked at the space above the stator 6 from the diagonally downward direction. FIG. 2 is a cross-sectional view of the front retainer in the area indicated by "A" in FIG. 1; FIG. 3 is a cross-sectional view at a different angle from FIG. 2; It is the figure which looked at the front retainer from the rear side. FIG. 3 is a cross-sectional view at a different angle from FIG. 2; It is a figure which shows the mode of a discharge port when a 1st cooling pipe and a 2nd cooling pipe are seen from a rotating shaft. (a) is a diagram schematically showing a first cooling pipe, a second cooling pipe, and a coil end to be cooled; (b) is a diagram schematically showing an example of an oil supply mode; It is a diagram showing.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

A configuration of an electric motor 1 employing a cooling structure 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is an axial view of a cooling structure 100 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view along line II-II shown in FIG. FIG. 3 shows the electric motor 1 with the front retainer removed from the state shown in FIG. In addition, the direction in which the rotating shaft CL1 of the electric motor 1 extends may be referred to as the "axial direction D1". Also, one side of the axial direction D1 may be referred to as "front" and the other side may be referred to as "rear". As shown in FIGS. 1 to 3, the electric motor 1 is provided with a mechanism for generating a rotational force inside a housing 2, and rotates a rotating shaft 3 with the generated rotational force. As shown in FIG. 2, the electric motor 1 includes a housing 2, a rotating shaft 3, a rotor 4, and a stator 6.

The housing 2 is a container that houses the rotating shaft 3 , the rotor 4 , the stator 6 and the cooling structure 100 . The housing 2 has a body portion 11 and a front retainer 12 . The body portion 11 has a substantially cylindrical peripheral wall portion 13 extending along the rotation axis CL<b>1 and a substantially disc-shaped end wall portion 14 that closes the rear opening of the peripheral wall portion 13 . The front retainer 12 is a substantially disc-shaped member that closes the opening at the front end of the peripheral wall portion 13 .

The rotating shaft 3 is a rod-shaped member extending along the rotating shaft CL1. The rotating shaft 3 is a member that is rotated by the torque generated by the electric motor 1 and transmits the torque to an external device. The rotating shaft 3 extends inside the housing 2 along the axial direction D1. The rotating shaft 3 has a front end supported by a front retainer 12 and a rear end supported by an end wall 14 . A front end of the rotating shaft 3 is rotatably supported by a front retainer 12 via a front bearing 16 . An oil seal 17 is provided on the front side of the front bearing 16 . A rear end portion of the rotating shaft 3 is rotatably supported by the end wall portion 14 via a rear bearing 18 . A resolver 19 is provided behind the rear bearing 18 . A resolver cover 20 is provided at a central position of the end wall portion 14 at a position spaced rearward from the rotating shaft 3 and the resolver 19 .

The rotor 4 is a cylindrical member that is provided on the rotating shaft 3 and rotates together with the rotating shaft 3 . The rotor 4 has permanent magnets arranged therein for forming a rotor magnetic field. Due to the interaction between the rotor magnetic field formed by the rotor 4 and the stator magnetic field formed by the stator 6, the rotor 4 rotates in conjunction with the rotary shaft 3 around the rotary axis CL1. For understanding of the structure, the rotor 4 and the stator 6 are shown in a simplified manner in the drawing.

The stator 6 is a member provided around the rotation axis CL1 with respect to the rotor 4 . The stator 6 has a stator core 21 and coils 22 . The stator core 21 is a member formed by laminating and welding electromagnetic steel plates in the axial direction D1. The stator core 21 is arranged in the space between the peripheral wall portion 13 and the rotor 4 . A coil 22 for forming a stator magnetic field is wound around the stator core 21 . A coil end 22a that is part of the coil 22 is formed at the front end of the stator core 21, and a coil end 22b that is part of the coil 22 is formed at the rear end. The stator core 21 is fixed to the housing 2 by stator bolt fastening portions 24 formed by fastening stator bolts at a plurality of positions around the rotation axis CL1 on the outer peripheral side (see FIG. 3). .

Next, the configuration of the cooling structure 100 according to this embodiment will be described. FIG. 4 is a view of the space above the stator 6 as seen obliquely from below. FIG. 4 shows a view from the viewpoint indicated by "V1" in FIG. As shown in FIG. 4, the cooling structure 100 comprises a first cooling pipe 30A and a second cooling pipe 30B. The first cooling pipe 30A and the second cooling pipe 30B are arranged in parallel above the stator 6 so as to extend in the axial direction D1. The first cooling pipe 30A and the second cooling pipe 30B are arranged so as to sandwich the uppermost stator bolt fastening portion 24 in the circumferential direction (see also FIG. 3).

As shown in FIG. 2, the first cooling pipe 30A extends parallel to the axial direction D1 from the front retainer 12 to the end wall portion 14 in the inner space of the housing 2 above the stator 6. there is A front end portion of the first cooling pipe 30A is connected to an insertion port of the front retainer 12 . Also, the rear end of the first cooling pipe 30A is connected to the insertion port of the end wall portion 14 of the housing 2 . The first cooling pipe 30A is supported by a support member 36 provided on the peripheral wall of the housing 2 at a position near the front end. Also, the first cooling pipe 30A is supported by a support member 37 provided on the peripheral wall of the housing 2 at a position near the rear end.

A plurality of discharge ports 50 for discharging oil (cooling medium) flowing through the first cooling pipe 30A are formed at a plurality of predetermined positions in the axial direction D1 of the first cooling pipe 30A. Thereby, the first cooling pipe 30A can cool the stator 6 by injecting oil to the stator 6 (the coil ends 22a and 22b and the stator core 21). The details of the configuration of the ejection port 50 will be described later. The second cooling pipe 30B also extends from the front retainer 12 to the end wall portion 14, like the first cooling pipe 30A. Also, a plurality of discharge ports 50 for discharging oil (cooling medium) flowing through the first cooling pipe 30A are formed at a plurality of predetermined positions in the axial direction D1 of the first cooling pipe 30A.

Now, with reference to FIG. 5, how the oil is supplied to the first cooling pipe 30A and the second cooling pipe 30B will be described. FIG. 5 is a cross-sectional view of the front retainer 12 in the area indicated by "A" in FIG. An oil passage 31A for the first cooling pipe 30A and an oil passage 31B for the second cooling pipe 30B are formed in the upper portion of the front retainer 12 . The oil passage 31A extends from the outer surface of the front retainer 12 to the insertion port 32A to which the front end of the first cooling pipe 30A is connected. Oil passage 31B extends from the outer surface of front retainer 12 to insertion port 32B to which the front end of second cooling pipe 30B is connected. The oil passages 31A and 31B intersect each other inside the front retainer 12, and an inlet oil passage 33 extending downward from the upper surface of the front retainer 12 communicates with the intersection. First, oil is pressure-fed by an oil pump (not shown) to the inlet oil passage 33, and the oil is supplied to the insertion ports 32A and 32B through the oil passages 31A and 31B, respectively. As a result, the oil is supplied to the cooling pipes 30A, 30B through the insertion ports 32A, 32B, respectively.

As shown in FIGS. 6 and 7 , the cooling structure 100 has a lubrication structure 110 that supplies oil to the front bearing 16 and oil seal 17 . FIG. 6 is a cross-sectional view at a different angle from FIG. FIG. 7 is a view of the front retainer 12 as seen from the rear side. As shown in FIG. 6, the front retainer 12 is formed with a thick portion 41 protruding into the housing 2 at the central position. The thick portion 41 is formed with a communication portion 43 that communicates from the outer peripheral side surface 41a to the inner peripheral side surface 41b. The communicating portion 43 opens in the space SP1 between the oil seal 17 and the front bearing 16 on the inner peripheral side surface 41b. Further, the front retainer 12 is formed with a plurality of strength ribs 42 extending continuously radially from the thick portion 41 toward the outer circumference (see FIG. 7). Each strength rib 42 protrudes into the housing 2 and radially extends from the thick portion 41 toward the outer periphery.

With the above configuration, some of the oil ATF leaks from the insertion openings 32A and 32B in the upper portion of the front retainer 12 and flows along the strength ribs 42 to the thick portion 41 (see FIG. 7). Then, the oil ATF flows into the communication portion 43 along the outer peripheral side surface 41 a of the thick portion 41 . As a result, the oil ATF is supplied from the communication portion 43 to the space SP1 to lubricate the oil seal 17 and the front bearing 16 .

As shown in FIG. 8, the cooling structure 100 has a lubrication structure 120 that supplies oil to the rear bearing 18 . FIG. 8 is a cross-sectional view at a different angle from FIG. The end wall portion 14 of the housing 2 is formed with an insertion port 38A for the first cooling pipe 30A and an oil passage 47 communicating with the insertion port 38A and extending radially inward. . The oil passage 47 communicates with the space SP2 between the resolver 19 and resolver cover 20 . Therefore, the oil ATF flows from the first cooling pipe 30A to the oil passage 47 via the insertion port 38A. Then, the oil ATF flows through the oil passage 47, is supplied to the space SP2, and accumulates in the space SP2. The oil ATF accumulated in the space SP2 overflows from the gap between the rotary shaft 3 and the housing 2, reaches the rear bearing 18, and lubricates it.

Between the insertion port 38A and the oil passage 47, a narrowed portion 48 having a diameter smaller than that of the insertion port 38A is formed. This limits the amount of oil ATF flowing to the rear bearing 18 . Therefore, the internal pressure of the first cooling pipe 30A can be maintained high, and the discharge pressure of the discharge port 50 can be ensured. The second cooling pipe 30B is also provided with a similar insertion port and oil passage, but is not formed with a constricted portion.

Next, the configuration of the discharge ports 50 of the first cooling pipe 30A and the second cooling pipe 30B will be described. As shown in FIG. 4, three discharge ports 51A, 52A and 53A are respectively formed at predetermined positions in the axial direction D1 of the first cooling pipe 30A. Three discharge ports 51B, 52B, and 53B are respectively formed at predetermined positions in the axial direction D1 of the second cooling pipe 30B. A combination of discharge ports 51A, 52A, 53A, 51B, 52B, and 53B is formed at a plurality of locations in the axial direction D1 of the cooling pipes 30A and 30B.

Here, the arrangement and diameter of the ejection ports 51A, 52A, 53A, 51B, 52B and 53B will be described with reference to FIG. FIG. 9 is a diagram showing discharge ports 51A, 52A, 53A, 51B, 52B, and 53B when the first cooling pipe 30A and the second cooling pipe 30B are viewed from the rotation axis CL1. Specifically, a reference line SL passing through the center of the first cooling pipe 30A and the center of the second cooling pipe 30B when viewed from the axial direction D1 is set. A line-of-sight direction D2 that is perpendicular to the reference line SL when viewed from the rotation axis CL1 is set. This line-of-sight direction D2 is one of the radial directions. FIG. 9 is a schematic view of the first cooling pipe 30A and the second cooling pipe 30B viewed from the viewing direction D2.

As shown in FIG. 9, when the first cooling pipe 30A and the second cooling pipe 30B are viewed from the radial direction (line-of-sight direction D2 in FIG. 2), the diameter of the discharge port 50 increases with increasing distance from the rotation axis CL1. In the first cooling pipe 30A, a discharge port 51A, a discharge port 52A, and a discharge port 53A are formed in order from the rotation axis CL1. Therefore, the diameter of the discharge port 51A, the discharge port 52A, and the discharge port 53A increases in this order, and the amount of oil discharged also increases in this order. In this case, a discharge port 51A, a discharge port 52A, and a discharge port 53A are formed, the diameter of which increases with increasing distance from the stator bolt fastening portion 24 (see FIG. 3). In the second cooling pipe 30B, a discharge port 51B, a discharge port 52B, and a discharge port 53B are formed in order from the rotation axis CL1. Therefore, the diameter increases in the order of the discharge port 51B, the discharge port 52B, and the discharge port 53B, and the discharge amount of oil also increases in this order. In this case, a discharge port 51A, a discharge port 52A, and a discharge port 53A are formed, the diameter of which increases with increasing distance from the stator bolt fastening portion 24 (see FIG. 3). The distance from the rotation axis CL1 is defined by the separation distance from the rotation axis CL1 in the direction D3 perpendicular to the rotation axis CL1.

A plurality of discharge ports 51A, 52A, and 53A formed at predetermined positions in the axial direction D1 of the first cooling pipe 30A are formed at different positions in the axial direction D1 with respect to other adjacent discharge ports. In the present embodiment, the discharge port 52A is formed at a position on the front side in the axial direction D1 with respect to the adjacent discharge port 51A. 53 A of discharge ports are formed in the position of the rear side in the axial direction D1 with respect to 52 A of adjacent discharge ports. Note that the ejection port 51A and the ejection port 53A, which are not adjacent to each other, are arranged at the same position in the axial direction D1. Thus, the outlets 51A, 52A, and 53A are alternately arranged in the axial direction D1. However, the ejection port 51A and the ejection port 53A may be arranged at different positions in the axial direction D1. Note that the amount of deviation in the axial direction D1 may be adjusted within a range of, for example, about 2 mm. The positional relationship of the ejection port 51B, the ejection port 52B, and the ejection port 53B in the axial direction D1 is the same as that of the ejection port 51A, the ejection port 52A, and the ejection port 53A.

Next, with reference to FIG. 10, the directions in which the oil is injected from each discharge port by the first cooling pipe 30A and the second cooling pipe 30B will be described. FIG. 10A is a diagram schematically showing the first cooling pipe 30A, the second cooling pipe 30B, and the coil ends 22a to be cooled. In FIG. 10A, a reference line SL2 extending vertically through the rotation axis CL1 is set. Also, a reference line SL3 passing through the rotation axis CL1 and the center of the first cooling pipe 30A is set. Also, a reference line SL4 passing through the rotation axis CL1 and the center of the second cooling pipe 30B is set.

The first cooling pipe 30A is arranged at a position where the reference line SL3 forms an arbitrary angle (here, 19°) in the range of 17 to 21° with respect to the reference line SL2. The second cooling pipe 30B is arranged at a position where the reference line SL4 forms an arbitrary angle (here, 7°) in the range of, for example, 5 to 9° with respect to the reference line SL2.

The angles of the ejection directions JD1, JD2, and JD3 by the ejection port 51A, the ejection port 52A, and the ejection port 53A of the first cooling pipe 30A will be described. The ejection direction JD1 of the ejection port 51A is set at an arbitrary angle (here, 43°) in the range of 39° to 47°, more preferably 41° to 45°, for example, with respect to the reference line SL3. The ejection direction JD1 of the ejection port 51A is preferably set in a direction that crosses the reference line SL2. The ejection direction JD2 of the ejection port 52A is set at an arbitrary angle (here, 7°) in the range of, for example, 3 to 11°, more preferably, for example, 5 to 9° with respect to the reference line SL3. The ejection direction JD3 of the ejection port 53A is set at an arbitrary angle (here, 52°) in the range of 50 to 54°, more preferably 51 to 53°, for example, with respect to the reference line SL3.

The angles of the injection directions JD1, JD2, and JD3 by the outlet 51B, the outlet 52B, and the outlet 53B of the second cooling pipe 30B will be described. The ejection direction JD1 of the ejection port 51B is set at an arbitrary angle (here, 22°) in the range of 18 to 26°, more preferably 20 to 24°, for example, with respect to the reference line SL4. The ejection direction JD1 of the ejection port 51B is preferably set to a direction that crosses the reference line SL2. The ejection direction JD2 of the ejection port 52B is set at an arbitrary angle (here, 35°) in the range of 31 to 39°, more preferably 33 to 37°, for example, with respect to the reference line SL4. The ejection direction JD3 of the ejection port 53B is set at an arbitrary angle (here, 54°) in the range of 52 to 56°, more preferably 53 to 55°, for example, with respect to the reference line SL4.

In order to change the cooling performance for the object to be cooled (coil end 22a) in the axial direction D1, the injection direction JD1 of the discharge port of the cooling pipe on the welding side and the discharge ports 30A and 30B of the cooling pipe on the opposite welding side , JD2 and JD3 may be different. For example, for the second cooling pipe 30B, when the injection direction JD3 of the discharge port on the opposite side of the welding side in the axial direction D1 is set at 54° with respect to the reference line SL4, the injection direction of the discharge port on the welding side in the axial direction D1 is The direction JD3 may be set at 57° with respect to the reference line SL4 (eg, any angle in the range of 55-59°, more preferably 56-58°, for example). As a result, the coil end 22a on the welding side is cooled more because the oil is injected over a wider area than on the opposite side. The injection direction can be similarly adjusted for other cooling pipes and other outlets.

FIG. 10(b) is a diagram schematically showing an example of an oil ATF supply mode. FIG. 10(b) shows only the supply mode of the second cooling pipe 30B. As shown in FIG. 10(b), the second cooling pipe 30B can supply the oil ATF in a wide supply area PE1 of the heat generating portion on the front side of the reference line SL2. In addition, the second cooling pipe 30B can supply the oil ATF in the supply area PE2, which is a part of the heat generating section, on the opposite side of the reference line SL2.

Next, functions and effects of the cooling structure 100 for the electric motor according to the present embodiment will be described.

A cooling structure 100 for an electric motor 1 according to this embodiment includes a first cooling pipe 30A and a second cooling pipe 30B arranged in parallel on the upper side of a stator 6 so as to extend in the axial direction D1. A plurality of discharge ports 50 for discharging the cooling medium flowing through the pipes are formed at predetermined positions in the axial direction D1 of the first cooling pipe 30A and the second cooling pipe 30B. Therefore, each of the first cooling pipe 30A and the second cooling pipe 30B discharges the cooling medium from the plurality of discharge ports 50, thereby supplying the cooling medium to the heat generating portion at a plurality of locations. can be done. Here, when the first cooling pipe 30A and the second cooling pipe 30B are viewed from the radial direction, the diameter of the discharge port 50 increases with distance from the rotation axis CL1. Therefore, the discharge amount can be increased as the discharge port is farther from the rotation axis CL1. In this case, the first cooling pipe 30A and the second cooling pipe 30B can secure the supply amount of the cooling medium at locations where the cooling medium is less likely to flow. As described above, it is possible to improve the uniformity of cooling of the heat generating portion.

For example, in the case of EVs and FCVs, since the motor is the main driving force, the amount of heat generated by the motor increases. Therefore, there is a problem that the motor performance (continuous output) is degraded unless the heat-generating portion inside the motor is uniformly cooled. On the other hand, in the present embodiment, by improving the uniformity of cooling of the heat-generating portion, it is possible to expand the range of use of the motor and improve the electric/fuel consumption and vehicle running performance.

At least three discharge ports 50 may be formed at predetermined positions in the axial direction D1 of the first cooling pipe 30A and the second cooling pipe 30B. In this case, the first cooling pipe 30</b>A and the second cooling pipe 30</b>B can suitably adjust the supply mode of the cooling medium to the heat-generating part with at least three outlets 50 .

A plurality of discharge ports 50 formed at predetermined positions in the axial direction D1 of the first cooling pipe 30A and the second cooling pipe 30B are located at different positions in the axial direction D1 from other adjacent discharge ports 50. may be formed. In this case, it is possible to suppress a decrease in the strength of the first cooling pipe 30A and the second cooling pipe 30B due to the adjacent discharge ports 50 being close together.

The invention is not limited to the embodiments described above.

For example, the shape, size, or arrangement of the ejection port is not limited to the above-described embodiments. The number of ejection openings formed at one location is not three as in the embodiment, but may be more than three or two.

DESCRIPTION OF SYMBOLS 1... Electric motor 2... Housing 3... Rotating shaft 4... Rotor 6... Stator 30A... First cooling pipe 30B... Second cooling pipe 50, 51A, 52A, 53A, 51B, 52B, 53B …outlet.

Claims (3)

A cooling structure for an electric motor that cools an electric motor including a rotating shaft extending along a rotating shaft, a rotor provided on the rotating shaft, and a stator provided around the rotating shaft with respect to the rotor,
A first cooling pipe and a second cooling pipe arranged in parallel so as to extend in the axial direction above the stator,
A plurality of discharge ports for discharging a cooling medium flowing through the pipes are formed at predetermined positions in the axial direction of the first cooling pipe and the second cooling pipe, respectively;
A cooling structure for an electric motor, wherein, when the first cooling pipe and the second cooling pipe are viewed in a radial direction, the discharge port has a larger diameter as the distance from the rotating shaft increases. 2. The motor cooling structure according to claim 1, wherein at least three of said discharge ports are respectively formed at predetermined positions in said axial direction of said first cooling pipe and said second cooling pipe. The plurality of discharge ports formed at predetermined positions in the axial direction of the first cooling pipe and the second cooling pipe are formed at different positions in the axial direction with respect to other adjacent discharge ports. The cooling structure for an electric motor according to claim 1 or 2, wherein

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